Square Bodies

rusty6 · Oct 23, 2022

The 73 to 87 GM truck body design has come to be known as square body lately and also rather collectible. Those trucks were everywhere for years but now its getting hard to find many that are not rusted through. My 81 is one of the few I know of locally. A former diesel powered truck it has had the 403 Olds gas engine since 1986 and been a steady and reliable performer. Might be my imagination but it seems to have a slight miss when the engine is cold. I installed a new set of
delco spark plugs but not sure it changed much. The plug wires are not old so I'm assuming they are ok. Rest of the ignition parts are original to the 1980s. Some video of it here.

81 Sierra Classic

d9gdon · Oct 23, 2022

That's a nice looking truck with a unique engine in it, that's for sure. I'm curious as to that Oldsmobile engine choice...obviously it was readily available?

Most of the 6.2L diesels in our neck of the woods were repowered with either a 350 or a 454.

I have a 1983 GMC High Sierra C20 in solid copper that was a 454 when new. I bought it minus the engine last year. I'm going to go back with a 396 in it since I have one. This one is a manual transmission. I actually bought it to strip the body parts and use on my other one, but decided I wanted to fix it up too.

I also inherited my brother's pickup. It's a 1982 Silverado C20 with 454 and automatic, in white with a red cab top.

The square body pickups have definitely gotten hot in the last couple of years.

rusty6 · Oct 23, 2022

(quoted from post at 16:39:47 10/23/22) That's a nice looking truck with a unique engine in it, that's for sure. I'm curious as to that Oldsmobile engine choice...obviously it was readily available?

=.

The big advantage of the Olds gas engine is that it was literally a bolt in replacement for the 350 diesel in these pickus. Anything from the 307 up to the 455 Olds would work but in 86 those gas engines were in such demand that I had to take the first one readily available. I'd wanted a 350 but this 403 was at the wreckers. I have no regrets on that choice.

Bob Bancroft · Oct 23, 2022

In 1977 I got a brand new company truck. GMC heavy half ton with 350 V8 and four speed truck transmission. This was a big deal because it was the first truck we had which didn't have a six cylinder and 'three on the tree'. Now the same dealership has 3/4 ton 4x4's, duallies, and multiple roll backs, to do less work.

white halftrack · Oct 23, 2022

Very nice looking truck.

Olfolks · Oct 23, 2022

We did a lot of the diesel to gas conversions for a fellow who would buy the diesel repos off the bank for Pennies on the dollar then pay us
to put a gasser in them, we started with the 350 olds but ended up doing some 403s and 307s because every one else was doing the same
and the gas engines were getting hard to find. The last one we did was a early model diesel to a late model diesel olds engine which was way
harder than switching to a gas

rusty6 · Oct 23, 2022

(quoted from post at 17:56:01 10/23/22) We did a lot of the diesel to gas conversions The last one we did was a early model diesel to a late model diesel olds engine which was way
harder than switching to a gas

This 350 diesel to Olds gas was so simple. As I recall the only change I had to make was to use the diesel water pump on the gas engine. Everything else just bolted on where the diesel used to be. Dual exhaust system too.

55 50 Ron · Oct 23, 2022

Rusty,

Did you do the engine swap yourself? You have a real knack to get these classic photos. Is that wheat stubble or maybe canola? I may be wrong, but I think it's wheat stubble.

Dieseltech · Oct 23, 2022

I had a 1979 that I had switched it to the 455 Olds V-8, that I ran on LP gas. I then put in another 455 that was set up for a turbo using LP. That was a fun truck to drive as I left the diesel emblem on the tailgate. Close following drivers would think they could pass easily, but quickly changed their mind when I felt ornery and floored the go pedal.

rusty6 · Oct 23, 2022

Dieseltech wrote:
(quoted from post at 18:50:46 10/23/22) I had a 1979 that I had switched it to the 455 Olds V-8, that I ran on LP gas. I then put in another 455 that was set up for a turbo using LP. That was a fun truck to drive as I left the diesel emblem on the tailgate. Close following drivers would think they could pass easily, but quickly changed their mind when I felt ornery and floored the go pedal.

Sounds like a fun truck. When the original diesel mufflers finally rusted out on mine I had them replaced by a pair of red bottles which give it the awesome sound that I've always wanted.
Duals

rusty6 · Oct 23, 2022

(quoted from post at 18:49:41 10/23/22) Rusty,

Did you do the engine swap yourself? You have a real knack to get these classic photos. Is that wheat stubble or maybe canola? I may be wrong, but I think it's wheat stubble.

Hi Ron, yes, nice thick wheat stubble in the pic. And yes, I did most of the swap myself in an unheated garage in winter so that tells you it was pretty basic. I had my brother come along to help with some of the heavy lifting and fine tuning.

RBnSC · Oct 24, 2022

We had a bunch of diesels like that Dad had one exactly like that one. had the 6.0 never gave trouble. I did have to go pull the injector pump and have it rebuilt to get it home. It was under a pole shed about two hours away.
my FIL had an 81 We put head gaskets on it four times then he finally put a gas motor in it.
we had about nine cars and trucks that had 5.7 diesels and i had a cutless ciera with a v6. those were busy years for me.
Ron

rusty6 · Oct 24, 2022

(quoted from post at 07:28:08 10/24/22) We had a bunch of diesels like that=
we had about nine cars and trucks that had 5.7 diesels and i had a cutless ciera with a v6. those were busy years for me.
Ron

There were a few locals that had good luck with the 350 diesels in pickups and got a lot of years of economical driving out of them. But seems the majority of these 350 diesels were subject to head leaks and eventually replaced with gas motors. If you drove them like a car they'd last but if you worked them like the typical farm truck they gave problems.

glennster · Oct 24, 2022

heres my old truck, started out as a 73 chevy heavy half, did a rebuild in the early 80s due to rust. used front end, replaced the bed too. motor was replaced with a 69 nova 350/350hp, .30 over, trw 8.5 to 1 , lots of go fast goodies. its retired at the farm now.

glennster · Oct 24, 2022

dang pic didnt post

Leroy · Oct 25, 2022

Had a 74 half ton That Dad got from a cousin of his and had the cak rebuilt. Did not want a second pickup so got rid of bed. It was the 350 V8 automatic. I built a wood flat bed for it. Late wife sold it about 12 years ago after I had heart problems when she thought I would no longer have use for it. Wish I would still have it and the 70 GMC half ton. That had the 307 automatic and started having running problems that no one coulf figure out Later found it was partially expermintial soln to GME dealer for work truck to see how things would work. NO one could find carb parts, turned out it had a special mannifold that had a Dodge carb put on so that is whu do mody could find carb parts, The defroster was made so it took the core for a truck with AC that ours did not have.

d9gdon · Oct 25, 2022

I did not remember that the 1981 models came with the 5.7L Olds diesel instead of the 6.2L that came out in 1982.

I drove a 5.7L Olds diesel powered pickup in a 1980 model half ton and it was pretty underpowered to a 16 year old back then...ugh.

Square Bodies

rusty6

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d9gdon

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rusty6

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Bob Bancroft

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white halftrack

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Olfolks

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rusty6

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55 50 Ron

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Dieseltech

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rusty6

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rusty6

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RBnSC

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rusty6

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